1. Field of the Invention
This invention relates to a detonator for use in setting off an explosive charge, and to a method of setting off an explosive charge.
2. Background Information
Detonators are used extensively in mining and quarrying. In use, a detonator is arranged in close association with a primer. The detonator has a fuse which detonates the primer, the primer in turn causes the charge to explode. It is often desirable to set off a series of explosive charges sequentially, with accurate, split-second timing between explosions. An arrangement for effecting such sequential detonation is referred to as a sequential detonics train.
Existing detonators utilize either a cord which is ignited and burns, or a fuse wire which is ruptured by passing an electrical current therethrough. In the cord type of detonators, timing is determined by the length of the cord and the speed at which it burns. They have the disadvantage that timing can often not be controlled accurately enough and that a burning cord is not acceptable in certain environments such as, for example, in coal mines where there is the risk of gas explosions. In the fuse wire type of detonators, timing is usually provided by electronic means. A drawback of some known fuse wire type detonators is that they require long lengths of insulated, relatively heavy gauge copper wire running from the source of current that is used to rupture them. The wire is costly and the copper as well as the insulation ends up as impurities in the ore that is being mined, and as such is unwanted.